1. Field of the Invention
This invention relates to a method and apparatus for measuring transmitted optical distortion in glass sheets.
2. Background Art
Manufacturers of glass sheets, particularly glass sheets formed into various curved shapes for use as automotive windshields and backlites, are interested in measuring and evaluating the amount of optical distortion in the formed sheets that might be perceived by a human observer, such as the operator or passenger in a vehicle in which the glass may be mounted as the windshield or backlite. One of the problems associated with evaluating the glass sheets is that surface markings or elements, such as the metal heating/defrosting element typically affixed to backlites, may complicate or even corrupt the distortion analysis if the marking/element is not identified and isolated from the distortion analysis.